ARPSNMP

arpsnmp - keep track of ethernet/ip address pairings

arpsnmp [

arpwatch - keep track of ethernet/ip address pairings

arpwatch [ -d ] [ -f datafile ] [ -i interface ]

[ -r file ]

Arpwatch keeps track for ethernet/ip address pairings. It syslogs activity and reports certain changes via email. Arpwatch uses pcap(3) to listen for arp packets on a local ethernet interface.

The -d flag is used enable debugging. This also inhibits forking into the background and emailing the reports. Instead, they are sent to stderr.

The -f flag is used to set the ethernet/ip address database filename. The default is arp.dat.

The -i flag is used to override the default interface.

The -r flag is used to specify a savefile (perhaps created by tcpdump(1) or pcapture(1)) to read from instead of reading from the network. In this case, arpwatch does not fork.

Note that an empty arp.dat file must be created before the first time you run arpwatch.

Here’s a quick list of the report messages generated by arpwatch(1) (and arpsnmp(1)):

new activity

This ethernet/ip address pair has been used for the first time six months or more.

new station

The ethernet address has not been seen before.

flip flop

The ethernet address has changed from the most recently seen address to the second most recently seen address. (If either the old or new ethernet address is a DECnet address and it is less than 24 hours, the email version of the report is suppressed.)

reused old ethernet address

The ethernet address has changed from the most recently seen address to the third (or greater) least recently seen address. (This is similar to a flip flop.)

changed ethernet address

The host switched to a new ethernet address.

/usr/operator/arpwatch - default directory
arp.dat - ethernet/ip address database
ethercodes.dat - vendor ethernet block list

arpsnmp(8), arp(8), bpf(4), tcpdump(1), pcapture(1), pcap(3)

Craig Leres of the Lawrence Berkeley National Laboratory Network Research Group, University of California, Berkeley, CA.

The current version is available via anonymous ftp:

ftp://ftp.ee.lbl.gov/arpwatch.tar.Z

Please send bug reports to arpwatch@ee.lbl.gov.

Attempts are made to suppress DECnet flip flops but they aren’t always successful.

Most error messages are posted using syslog.